Basic actions e.g. note velocity/volume

There are several ways to adjust the velocity of midi notes, but this won't just affect the transient, it will apply for the entire note (subject to the natural decay of the patch)
 
I'm sorry I'm not at my DAW at the moment, but I think you need to look in the Edit menu where you'll find Select by Filter. Start by unchecking everything, then just check notes, then apply the minimum & maximum values.
this will then only select those notes falling within your particular criteria
 
From there you can set them all to a given value in the Event Inspector

You can open the piano roll view and draw the velocity controller. Or under Process there is Scale Velocity. Both are shown here:

 
As to adjusting the velocity for playing I found the Gain in the console strip works.
 

 
I'm sure there are other ways as well.

Referring to the first picture by DrLumen, you can use this technique in conjunction with the Edit > Select by Filter function in order to have only those notes falling below your threshold highlighted so only those notes can be dragged upwards/downwards.
 
Or you can use Scale Velocity again on your restricted selection
 
Or.... you can select the desired notes as described, then in Track View, right click the clip containing the notes and choose Process Effect > Midi Effects > Cakewalk Fx > Velocity. This will open up the plugin's gui where you can do all sorts of things with velocity - it's a very powerful tool but it is also a destructive process meaning once you save your project without hitting undo, you'll lose the original velocities.
 
Also, you might find the Velocity plugin is mapped to Uncategorized instead of Cakewalk Fx as  outlined above.

"adjust a track (or a section of one) such that no note attacks are below a certain velocity" -- that's really all I'm after here, folks. Can't find the velocity controller or figure out Scale Velocity. DrLumen's Console view doesn't resemble mine.  
 
I'm reading "To edit velocity" in the program's Help. It gives 5 incomprehensible steps e.g. "2. Make sure Velocity has a checkmark next to it in the Show/Hide MIDI Events menu." No doubt the latter is in there somewhere, but it doesn't respond to any of my searches.
 
Thank you ALL for your ongoing input. There has to be a very simple answer somewhere -- I feel it in my bones.
 
 

OK, to be more precise:
1. Select clip or part of clip.
2. Choose Process > Find/Change in the main menu.
3. In the first dialog, enter (for example) 60 as the Max for Velocity, and OK.
4. In the second dialog, enter 60 as both the Min and Max for Velocity, and OK.
 
All notes with a velocity at or below 60 will be set to 60.

I was referring to Process > Find/Change.

Initially trying what you said, weak notes were still weak and faint on the screen. Volume knob is up. Trying different strategies in that popup brings results that refuse to show any logic. I can get it to play very softly or loudly this way (and variations there of I've been trying), whether changing Begin to 111 and End to 67, then vice versa or setting them both high or both low -- yes, checking Percentages (though I tried it without as well). 
 
Why can't there be a simple control for this within sight of the word Velocity? That's all I want to adjust. 
 
Find/Change does not show under Process, Brundlefly. 

It would be a very easy CAL program.    
 
Something like,
 
Get My_minimum_note_velocity
 
foreach Event where event type = NOTE if note.velocity < my_minimum then (= note.velocity  My_minimum). 
 
If you know anything at all about programming take a look at some of the samples provided in Cal Scripts, and modify. 

In Platinum, Ctrl-F1 should take you to the Cal scripts directory (At least on mine...)    Identify the directory, use Notepad (windows) or some text editor to create a simple text file with .cal as the ending, place in that directory.  Then access by Ctrl-F1.
 

brundlefly
Just noticed you are using S7. Back then, Process > Find/Change was Edit > Interpolate.
 
Note that 'Gain' on MIDI tracks is actually Velocity Offset. This can be used to quickly increase the Velocity of a whole clip by a fixed amount. But selectively adjusting just the lower limit is a special case that requres more steps.
 

 
Not on mine, though Process > Interpolate brings up the same "Event Filter -- Search" screen as in Bristol's reply #1 above. OK, I do Ctrl-A and go to that screen and set it for notes of 0 to 90 velocity, because I want all of those to be set at 90. Before I screw it up again, exactly what do I do in the little Scale velocity popup to get that result -- no velocities less than 90, nothing above 90 affected by the change? 
 
Velocity offset sounds great for when I need it some other time. 
 
I think we're on to something here. Thanks for sticking with me, gang. [EDITED/CORRECTED]

DrLumen
IMS from the CW 7-8 versions, once the notes are selected from the filter selection, set both begin and end (min/max) to 90 (not percent) in the Scale Velocity popup.

That just sets them all to 90. That was settled in reply #1, but it's good to have a 2nd route to doing so. I see now that Scale Velocity is for setting a crescendo or diminuendo. Does anybody have an idea how to up the velocity of, say, only the notes 90 or lower velocity? In attack, not tempo.  
 
I just tried going back to Event Filter - Search and unchecked absolutely everything except the Note parameter -- top line. Tried setting Velocity there to Min 0 and Max 90; clicked OK but it just took me to an almost identical Event Filter -- replace popup. I tried clicking Cancel and it gave me the same screen again. Hit Cancel again and it was gone. Went back and checked the parameters I'd unchecked -- it similarly resisted closing the popup before doing so.  
 
I've hit the C key many times by accident (aiming for the space bar) and now see it brings up a graph of the velocity. Help says this is for editing such, but I don't see how -- and the bottom of the graph isn't even visible. 
 
In Help I see under Process-Interpolate 
Velocity
 
From 0 to 127
 
From 80 to 127
 
Compresses the velocity values into a narrower range
 
We're getting warmer, but that still isn't it if it means it narrows everything proportionately. 
 
More frustration: Doing View > Console, sliders for the present track stack (Audio 1 and 2, MIDI 1 and 2) shows for a test track I've just created and the record button is red, just right. But all sliders are set in the same position -- about 1/6 of the way from the top. The one for my present MIDI 1 track appears to be for duration -- it's numbers range from 0 to 127. What's it mean? What to do here? 
 
NEXT DAY OCT. 4......... OK, the thin vertical line that accompanies each note in Player Piano View isn't a stem as I'd thought but a velocity indicator. Found this on trying Scale Velocity again. Opened the little popup and setting it for Begin: 80 and End: 100. This simply reset the velocities as a crescendo (from 80 to 100) from the beginning of the selected passage (they whole test piece) to the end -- you could see it in the rising row of vertical pinstripes.
 
Now accepting theories as to why there's no Velocity knob in Console view on mine. There really isn't! 
 

Okay, one more time with feeling...
 
Going back to what I posted earlier, and substituting 'Edit > Interpolate' for 'Process > Find/Change', and using the minimum value of 80 you mentioned above, this should do exactly what you described:
 
1. Select clip or part of clip.
2. Choose Edit > Interpolate in the main menu.
3. In the first dialog, enter 80 as the Max for Velocity, and OK.
4. In the second dialog, enter 80 as both the Min and Max for Velocity, and OK.
 
All notes with a velocity at or below 80 will be set to 80.

Glad you sussed it out.
 
Incidentally, if you want to preserve the relative value of your velocities after doing the Edit > Interpolate thing, then opening the Scale Velocity box, you could set both boxes to say, 140, tick percentages and all the selected notes will go up by 40%

The Velocity MIDI FX you mentioned in post #11 is primarily for altering velocity non-destructively on playback. The advantage of this is that you can experiment with different settings without permanently altering what you originally recorded. If necessary, it can be applied destructively once you're satisfied with the result, or it can be left active indefinitely.
 
In this case I don't think it can do exactly what you want, but you can hit F1 with focus on the FX dialog to bring up the Help on how the settings work.
 
You might want to consider an upgrade to the current SONAR if you can swing it. So much has changed since S7 that it will be difficult for most users on the forum to help you effectively... even oldtimers like me.